U.S. Pat. No. 4,609,574 (published Sep. 2, 1986, J. R. Keryk et al, Dow Corning Corporation), disclosed that Si-bonded higher alkenyl groups, such as, for example, 5-hexenyl groups in organopolysiloxane compositions are more reactive than Si-bonded vinyl groups toward Si-hydrogen. The organopolysiloxanes containing higher alkenyl groups can be prepared by reacting an organopolysiloxane containing Si-bonded hydrogen with an .alpha.,w-diene, but multiple addition reactions always occur. The organopolysiloxanes containing higher alkenyl groups are therefore preferably obtained by reacting an .alpha.,w-diene in large excess with the silane containing Si-bonded hydrogen and subsequently this silane is hydrolyzed and equilibrated with an organopolysiloxane.
E. Lukevits et al, Zhurnal Obshchei Khimii, Vol. 56, 140-143, 1986 (Chemical Abstracts, Vol. 105, 226720 h, 1986) describe the hydrosilylation of alkenes and alkynes using dimethyl(2-thienyl)silane. The triple bond is more reactive here than the double bond.
Therefore, it is an object of the present invention to provide organosilicon compounds containing alkenyl groups which can be prepared in a simple process with high selectivity.